This invention relates, in general, to a device for removing molten solder from a surface, and more particularly, to a device for solder removal in semiconductor processing.
It is often necessary to remove solder from the surface of a substrate to which a defective integrated circuit chip is bonded and then removed. In flip-chip processing, a chip is directly bonded to solder pads on a substrate; if the chip is defective, it must be removed from the substrate, leaving behind nonuniform solder bumps. This solder must be removed before bonding a new chip with new solder, because the nonuniform solder bumps left after removal of the defective chip may cause shorts or opens.
The removal of solder from the substrate has been achieved by vacuum suction. Vacuum suction comprises the suction of solder by an apparatus that utilizes a heated nitrogen gas. This vacuum suction apparatus is undesirable because it is very complicated to make and use. The velocity and the temperature of the nitrogen must be optimized in order to melt and remove the solder. In addition, solder residue may be left at the substrate surface between solder pads, causing leakage or other undesirable electrical characteristics. Furthermore, a different size vacuum suction device must be made for each size chip, which can get very expensive.
Another method of removing solder from a substrate comprises using a copper powder cake. A copper powder cake is a sponge-like material formed by sintering copper powder or balls. The copper powder cake works like a sponge to remove solder from a substrate. The use of a copper powder cake is undesirable because the process of making the cake is complicated as well as expensive. Because the copper powder cake may not be reuseable, it would be desirable to provide a new and less expensive device for solder removal. The copper powder cake may also leave solder residue on the surface of the substrate between solder pads. Both of the above devices also do not leave controllable amounts of solder to provide a uniform surface for the new solder. Because both of the devices are undesirable to make and use, it should be appreciated that it would be desirable to provide an improved device for solder removal.
Accordingly, it is an object of the present invention to provide a new, improved device for solder removal.
Another object of the present invention is to provide a device for solder removal which does not leave solder residue between solder pads.
A further object of the present invention is to provide a device for solder removal which allows for a controllable amount of solder to be left on the solder pads.
An additional object of the present invention is to provide a device and method for making a device for solder removal.
Yet another object of the present invention is to provide an improved device for solder removal without utilizing vacuum suction.
Yet a further object of the present invention is to provide a device for solder removal which can be easily fabricated for different sizes of chips.
Still another object of the present invention is to provide a device for solder removal which removes more solder than the prior art.
Still a further object of the present invention is to provide a device for solder removal which is easy to manufacture and use.